Direct Mail spam. Even if this is something some businesses will pay for, and even if it isn't a lot of messages, it is still an annoyance.<p>Would there be 1,000 businesses willing to spend $1 million each to send a message to a million people? That's $1 billion. Can messages be targeted enough and give a good enough ROI? Will users be pissed off and dismiss businesses that put ads into their private inbox?<p>More negatives than positives, IMHO..